1. Field of the Invention
The present invention relates to metallurgical furnaces of the type utilized in the melting of aluminum and, more particularly, to such furnaces in which the source of melting heat comprises electrically powered silicon carbide resistance elements so arranged as to be capable of melting aluminum from its solid or room temperature state by irradiation with electromagnetic radiation.
2. Description of the Prior Art
The following United States patents illustrate various furnace arrangements for use in the melting of aluminum and other metals:
______________________________________ Patent No. Patent No. ______________________________________ 1,924,201 3,240,915 1,995,524 3,688,007 2,552,648 3,700,224 2,682,566 ______________________________________
The foregoing patents reveal that it is known to utilize electrically energized resistance elements in the melting of various types of metals in melting furnaces. The patents also reveal that aluminum in particular is difficult to melt by direct utilization of the electromagnetic energy produced by resistance heating elements because aluminum does not strongly absorb such radiation. Accordingly, it has been the practice, when using electrical resistance elements, to rely on the resistance elements primarily to heat the atmosphere residing in the furnace and to employ forced air circulation or the equivalent to deliver the heat energy to the aluminum which is to be melted. Examples of forced air circulation for the melting of aluminum with resistance heating elements appear in U.S. Pats. No. 1,924,201 and 1,995,524. U.S. Pat. No. 3,700,224 illustrates the use of electrically energized resistance elements in an aluminum melting furnace without forced air circulation. U.S. Pat. No. 3,688,007 illustrates the use of electrical resistance elements which are housed in a submersible, heat exchanging medium. In this latter patent, heat conduction, as opposed to direct electromagnetic irradiation, is being used. Prior to the present invention it has been generally thought not practical to utilize resistance heating elements such as silicon carbide elements for the melting of aluminum by direct irradiation of the aluminum.